Treatment of polyene compounds



Patented Nov. 12, 1946 TREATMENT OF POLYENE COMPOUNDS Anderson W. Ralston, Chicago, and Otto Turinsky, Palatine, Ill., assignors to Amour and Company, Chicago, Ill., a corporation of Illinois No Drawing. Application January 22, 1942,

Serial No. 427,833

This invention relates to processes of treating unsaturated compounds, and it more specifically relates to the treatment of unconjugated, unsaturated organic materials, such as fats and fatty acids having two or more double bonds with aliphatic organic iodides whereby the unconjugated and unsaturated fats or fatty acids are converted to conjugated fats or fatty acids or to products having improved drying or resinifying properties. a

It has hitherto been recognized that the chemical properties of unsaturated organic compounds having aplurality of double bonds depend not only upon the degree of unsaturation but also upon the relative position of the unsaturated bonds with respect to each other. If the unsaturated bonds are conjugated then the organic compound has properties characteristic of unsaturated compounds, and in addition, has those chemical properties characteristic of conjugated systems.

The distinction between conjugated and uhconjugated systems is well illustrated by comparing the chemical behavior of linolenic' acid and eleostearic acid. These acids are isomeric, straight chain fatty acids each containing three double bonds. It is believed that in linolenic acid the double bonds are in the 9-10, 12-13 and 15-46 position while in eleostearic acid they occupy the 9-10, 11-12 and 13--l4 positions. Thus in eleostearic acid the double bonds are conjugated. When linseed oil is used as a paint vehicle the paint dries quite differently than it would if tung oil acid were used. Eleostearic acid is thechief fatty acid constituent present in tung oil glycerides. Tung oil body-dries whereas linseed oil film-dries. Body-drying is much preferred and is believed to result from the fact that eleostearic acid is conjugated. Therefore, it is highly desirable that ways be developed by means of which unconjugated highly unsaturated compounds can be converted to conjugated, unsaturated compounds and thus gain the advantages inherent in conjugated systems.

The fact that the relativev position of double bonds in an alkyl chain can be changed by treatment with strong alkalies has been, known for some time. In Biochem. J. 31, 138 (1937) Moore reported that treatment of fats and fatty acids with alcoholic potassium hydroxide brings about a shift in the relative position of double bonds in an alkyl group and that thisshift is towards a conjugated configuration. Recently Kass and Burr, J. Am. Chem. Soc. 61, 3292 (1939) have shown that the time necessary to bring about this change Claims. (Cl. 260-4056) can be materially reduced by the use of high boiling organic solvents and strong alkalies. Other investigators have found that the alkali process may be improved by conducting the reaction in aqueous solution at elevated temperatures and pressures. However, any such process which employs alkali has inherent disadvantages. In order to conduct this process it is necessary that the fats or fatty acids be converted to soaps. The'se soaps must then be acidified in order to obtain the transformed fatty acids. Where one desires to conjugate an oil a number of steps are, therefore, necessary in order to produce satisfactory results by-these processes. It is necessary to first saponifythe fat and then to treat the soaps with strong caustic in order to bring about conjugation, acidify the resulting soaps, purify the fatty acids and finally re-esterify them with glycerine.

It would be extremely desirable to develop a process whereby theunconjugated fatty acids'or fats could be treated directly without the necessity of saponification or other chemical change. Such a process would be much easier to conduct on a commercial scale and would have a number of apparent advantages over the alkali processes for bringing about this transformation. Even before the introduction of the alkali methods various investigators have sought to find compounds which would produce the desired isomerization directly. For example, the Scheiber Patent No. 1,896,467 lists a number of compounds including sulfuric acid, ferrous iodide, chlorine, oxygen,

etc., for this purpose; but none of these compounds have proved effective or have come into commercial use.

We have now discovered a class of compounds which catalyticaily improve the drying or resinifying properties of unconjugated systems. It is believed that this improvement is attained by a change of the unconjugated, unsaturated system to a conjugated, unsaturated system although we cannot definitely state that all the improvement in drying properties is explained by, this transformation. The substances which we use to bringabout this transformation are used in relatively small amounts at elevated temperatures to impart conjugation to the unconjugated 'compound or Otherwise improve the drying properties.

- dene In the practice of our process we can use any compound which contains double bonds in un-- conjugated relation. Of the natural oils, linseed oil and soya bean oil are particularly susceptible to this treatment, and dehydrated castor oil and fish oil are also markedly improved by the treatment. Other .oils, such as 'cottonseed'oil, peanut o l, corn oil and other oils not ordinarilyregarded as drying oils, can alsobe treated by this procedure and their-drying characteristics substantially improved. Instead of treating the oils directly, we can hydrolyze the oils to obtain the natural mixtures of fatty acids and then subject the mixture to the treatment for producing conjugation. The conjugaed mixtures thusprepared may suitably be reacted with a polyhydric alcohol and a dibasic acid to form alkyd resins, or may be reesterifled with glycerol or the higher alcohols, such aspentaerythritol or dipentaerythritol to form synthetic glycerides having improved drying characteristics. I

Particularly in connection with the oils which are not normally classed as drying oils,.such'as cottonseed oil, vcorn oil, peanut oil, soya bean oil, etc., we find that especially good results can be obtained by first subjecting the acid mixture obtained from such an oil to fractional distillation andthen subjecting a relatively highly unsaturated fraction so obtained and containing a higher proportion of the polyene acids, to the catalytic treatment described above.

Another procedure includesfirst subjecting the acids obtained through hydrolysis of natural oils to solvent extraction whereby there is produceda portion which contains unsaturated acids in greater proportion than in the original acid mixture and then subjecting this portion to catalytic treatment as before described, or additional benefits may be obtained by first fractionally distilling the acid mixture, treating the fraction so obtain'edbysolvent extraction, and then catalytically treating the resulting product using an allphatic organic iodide as the catalyst.

Though our improved process finds its greatest advantage in connection with those oils or We shall now give examples of how ourprocess Y can be practiced.

Ten parts by weight of linoleic acid containing approximately 25% of oleic acid is admixed with 0.023 part by weight of octadecyl iodide and the mixture heated advantageously in the presence of an inert gas, such as nitrogen; This mixture is heated at a temperature of about 200 C. fora value 28.5.

brief period of time, approximately about :three "to five minutes, and then heated at about 200 C. for a somewhat longer period oftime, approximately ten to twenty minutes. Thereafter the mixture iscooled advantageously .in the presence of the inert gas. Under these conditions the -,diene value is increased from an initial-value of,2 an to final value of 29.2, thus indicating that marked conjugation has been imparted to an otherwise unconjugated oil. The treated acid can be esterified in any well-knownway, andsuch esterified acids, when allowed to dry ;as a .film,

show the frosted film characteristics of tung-oil or similar conjugated oils.

' Example 2.

Thirty parts by weight of the linoleic acid of Example 1 are admixed with 0.06 partby weight of dodecyl iodide and the mixture heated for a For the first three minutes of theheating the-temperaturewas about.200 C. and thereafterabout 300- C. The diene value of the linoleic acid'before treatment wa's2 and after treatment was 31. 1

Example 3 Thirty parts by weight of refined andbleached soy bean oil are heated with 0.06 part by weight of dodecyl iodide for a period of -thirty-minutes at a temperature of 300 C. This results in increasing the-diene value, of the soybean. oilfrom 3 to 29. Similar results are obtained when-other unsaturated, unconjugated fats and fatty acids are subjected to the action of catalytic amounts of alkyl iodides at elevated temperatures.

Example 4 One-thousand parts of fatty acids obtained from sardine oil are distilled'under'reducedpressure and the fatty acids separated into cuts having different degrees of unsaturation. The first fraction obtained consists of approximately 30% of the original fatty acids andconsists essentially of myristic, palmitic and palmitoleic acid. The

second fraction obtained is approximately 250% of the original acid'and contains the highly unsaturated acid present in the original'fattyacid' This fraction consists of acids having a plurality of double bonds; usually two or'more'. Acids, such as clupanodonic, which is supposed .to-have five double bonds, are present in'this fraction. Approximately 500 parts of the highly unmixture.

saturated fatty acids obtained by fractionation are mixed with 0.4 part of dodecyl iodide and the mixture heated in a nitrogen atmosphere for twenty minutes at 280 C. The initial diene value;

of the acids was'found to be 2 and the final-diene Two-hundred and fifty parts .of the treated acids were mixed with 26 partsof glycerine and, i 2.7 parts of catalyst (p-toluenesulfonic acid) add- I ed. The mixture was placed in a round-bottom flask, swept out with nitrogen and heated for five hours at 125 C. A stream of nitrogen was passed through the flask during the heating period order to avoid oxidation. An equal volume of solvent (Skelly solve F) was then added,-and the acids removed by washing theoil layer with 17.0%

ethyl alcohol containing a small amount of KOH.

After the acids were removed the product was dried with anhydrous sodium sulfate 'and'the solvent removed under vacuum. The iodine value of the resulting triglyceride was 106, and the diene value 32.2.

A film of the triglyceride was placed on glass and observed. This film dried completely after.

thirtyesix hours, and showed no tackiness after this time. The dried oil mm wasquite opaque which is .characteristic of deep drying.

Example Exempted Two parts of indoform were added to 328 parts of extracted soybean oil and the mixture heated to 183 C. under an atmosphere of nitrogen with effluent stirring. After fifty minutes heating the oil reached a temperature of 165 C., at which temperature the refractive index started to increase rapidly. The heating was continuedfor anadditional hour, and the final temperature was 183 C. At the end of this period the rate of increase of the refractive index .Was quite small, and the heating was discontinued. The reaction mixture was then cooled .in an atmosphere of nitrogen. The resulting product was a pale, orange-yellow; non-bodied oil which had .the following constants: refractive index (n20) 1.4807, iodine value 115.0, diene value 21.8. The oil before treatment had the following constants: re-

.fractive index (mo) 1.4750, iodine value 134.4,

diene'value 1.5. The original soybean oil did not gel upon the addition of stannic chloride, whereas the treated oil formed a rubbery gel after .ten minutesoontact withstannic chloride. A major portion of this product was again treated with an additional 1 part of iodoform and heated for 1 hour at 183 C. The refractive index again rose during this second treatment and became essentially constant at the end of the heating period. The sample now showed the following constants: refractive index (n20) 1.4830, iodine value 99.4 and diene value 32.0. It formed a rubbery gel with stannic chloride after 1 minute contact. These results show that appreciable conjugation has been imparted to this oil by the above treatments.

Example 7 A mixture of 100 parts of extracted soybean constants: refractive index 1.4832, iodine value 96.6, diene value 25.8. The product formed a rubber-like gel 15 seconds after contact with stannic chloride. The original constants for this oil are given in the following example. These data show that appreciable conjugation has been brought about inthis oil by this treatment.

Example 8 y A mixture of 100 parts of the extracted soybean oil described in Example Band onegram of the I iodine addition productof indenc was heated to .185 under an atmosphere of nitrogen with ei'lluent stirring.- After 17 minutes heating the temperature rose to C. atwhich temperature there was a rapid rise in refractive index. No

further increase in refractive index was brought about by an additional fifteen minutes heating at 185. The mixture was then cooled in 9. nitrogen atmosphere and the following constants determined: refractive index (1120) 1.4840, iodine value 27.2. The oil gelled after one-half minute contact With stannic chloride. All of these observations show that appreciable conjugation has been brought about in this oil by theabove treatment. 1

Example 9 Two grams of iodine was dissolved in. 20 cc. of carbon disulfide. This was added gradually to a solution of 5 grams of turpentine in 10. cc. of carbon disulfide, and the mixture allowed to stand for two hours with frequent shaking. The solution turned from a .violet to brown during the course of the reaction.

The above solution was added extracted soybean oil, similar to that used in Example 6 and the resulting mixture was heated to 225 C. under an. atmosphere of nitrogen with stirring. The heating time was two hours and the maximum temperature was 225 C. The mixwas then cooled under an atmosphere of nitrogen. The product was pale yellow incolor and was not bodied. It had .the following analytical constants: refractive index (can) 1.4802, iodine value 106.8, diene value 24.0. The oil formed a rubbery gel with stannic chloride after ten minutes contact. These results show that appreciable conjugation has been brought about by this treatment. 1

The amount of catalyst required is small. The amounts given in the foregoing examples have been found to give good results but. still lesser quantities may be employed. More than the quantities stated can, of course, be used but this is wasteful and serves no useful purpose.

During the heating and cooling it is of special advantage to maintain the reaction mixture in' an inert atmosphere such as nitrogen or carbon dioxide as we have found that this practice yields a. product of a desired character having improved color and drying characteristics. However, our invention may be practiced. without this feature.

In many cases it is desirable to remove the catalyst but this is not always necessary and depends upon the particular use which is to be made of the conjuated oils. In those cases where it is desirable to remove the catalyst this can be accomplished by the usual method of caustic refining or by many of the standard methods employed for refining oils. In general weprefer not to remove the catalyst since its presence is usually not harmful.

We can operate at various times and temperatures. One of the characteristics of our invention is that conjugation is imparted quite rapidly, and this is a definite commercial advantage. Our oils and fatty acidscan be heated for longer periods of time, if,for example, it is desired to irnpart bodied characteristics to the oil rather than conclude the heat treatment after conjugation alone has been imparted to the oil or fatty acid. That is to say; conjugated, unsaturated fatty acids and glycerldes thicken when heated for to 328 grams of g "indicated in ou examples.

somewhat longer periods or time than we have Therefore, we can. of course, impart conjugation to the unsaturated compound during a relatively short period and continue the heating for a longer period of time,

up to two or three hours, if we wish to .body

the oil or fatty acid. 'Such thickened oils have much higher viscosity'than the simple conjugated fluid oils, and this may be the result of polymerization of the'conjugated material present. Therefore, we do not wish our invention to be limited to any particular time of heating. Those skilled in the art will understand different oils may require different heating periods and that the oil orfatty acid is to be heated until appreciable improvement in diene value is secured and that heat is to be discontinued before this product is bodied more than is desired.

Similar considerations apply with respect to temperature. At the temperature stated conjugation is imparted rapidly. Lower temperatures can be'used but with a relative slowing up in the ,reaction rate.

For example, We can operate at temperatures below 100 C. and under certain conditions this has been found to be advantageous. Obviously the temperature should not exceed the volatilization temperature of the material undergoing treatment, nor should it be so high as to decompose the oil or fatty acid. But within these operative limits any temperature can be chosen.

In the appended claims we refer to the catalyst as an aliphatic iodide having iodine linked to a carbon atom. This structure characterizes the various. iodides we use and distinguishes from the various amine hydroiodides which we have separately described and claimed in our co-pending application Ser. No. 427,832, filed January 22, 1942.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent i's:

1. The process of conjugating a polyene compound chosen from the group consisting of unconjugated polyene fats and fatty acids which comprises heating said polyene compound in the presence of an aliphatic iodide having iodine linked to a carbon atom, and discontinuing the heating after substantial conjugation has been effected, but before the thus conjugated po ene compound becomes substantially heat bodied.

2. The process as in claim 1 wherein the polyene compound is soy bean oil. 7

' 3. The process as in claim 1 wherein the polyene compound is linoleic acid.

4. The process as in claim 1 wherein the allphatic iodide is dodecyl iodide.

5. The process as in claim 1 wherein the polyene compound is heated to a temperature between about 200 C. and 300 C.

ANDERSON W. RALSTON. o'rro TURINSKY. 

